The overall objective of the proposed research is to examine the role of the uterine lysosome in ovum implantation. More specifically, we intend to determine the biochemical function of uterine lysosomal proteases during the cellular redifferentiation and autolysis of ovum implantation. The effect of implantation on uterine lysosomal enzyme activities will be determined. Protease inhibitors specific for lysosomal proteolytic enzymes, cathepsin B1, and D, will be used to determine the importance of changes in lysosomal protease activity to implantation. Further experiments will examine the hormonal control of the synthesis and degradation of uterine cathepsin D and the contribution of these processes to enzyme changes during implantation. An understanding of mechanisms of control of lysosomal protease activity in the uterus should contribute to our understanding of the processes of implantation and early placental development.